1. Field of the Invention
This specification relates to a liquid crystal display device module, and particularly, to a liquid crystal display device module capable of implementing a transparent display using reflection and transmittance properties of Cholesteric Liquid Crystal (CLC).
2. Background of the Invention
A Liquid Crystal Display (LCD) device is a flat panel display device which includes electrode lines aligned in the form of lattice on two transparent substrates facing each other, a liquid crystal display (LCD) panel with liquid crystal interposed between the substrates, a light source for emitting light to the LCD panel. Especially, cholesteric liquid crystal (CLC) has a plurality of thin molecular layers, in which molecules are aligned in a direction of a longer axis and whose surfaces are in parallel to one another so as to generally form a helical structure. When the cholesteric liquid crystal is used as the liquid crystal in the LCD panel, the LCD panel is allowed to have properties of selectively reflecting or transmitting light. Therefore, the use of the cholesteric liquid crystal is advantageous in implementing a transparent display.
However, in spite of those advantages, the LCD must have a separate light source because it does not emit light by itself, and accordingly, a non-transparent backlight unit is required at a rear surface of the LCD panel. Especially, a light guide plate included in the backlight unit serves to guide light when the liquid crystal of the LCD panel is driven so as to be evenly distributed on an entire region of the LCD panel, thereby increasing luminance of an image. However, the light guide plate itself lowers transparency of the LCD panel, which makes it difficult to implement a transparent display.
FIGS. 1A and 1B schematically show reflection and transmittance properties according to a module type of a transparent display according to the related art.
As shown in FIG. 1A, the related art transparent display may include an LCD panel 10, a backlight unit 30 for emitting light to a rear surface of the LCD panel 10, and a supporting structure 50 for securing those components to be modularized.
The transparent display having the configuration transfers light emitted from a light source 31 to the LCD panel 10 using a light guide plate and an optical sheets 33. The light functions as ambient light which facilitates an observer to identify an image (IMAGE) generated on the LCD panel 10 by a reflected light 1a. On the contrary, the light guide plate, the optical sheet 33 and polarizing films 17 attached on both surfaces of the LCD panel 10 lower the transparency of the LCD panel 10, and accordingly an incident light b1 is rarely transmitted through the LCD panel 10. As a result, it is difficult for the observer to identify an object (OBJ) located at a rear surface of the transparent display.
As a structure proposed for overcoming the disadvantage, FIG. 1B shows an example of removing the light guide plate and other optical members to increase transparency of the LCD panel 10. As shown in FIG. 1B, a transparent display with this configuration includes an LCD panel 10 formed the same as that shown in FIG. 1A. However, the LCD panel 10 does not have the polarizing films (17 in FIG. 1A) attached on both surfaces of the LCD panel 10 and the backlight unit (30 in FIG. 1A), merely supported and secured by the supporting structure 52.
Accordingly, most of light b2 incident onto the LCD panel 10 is transmitted through the LCD panel 10 without absorption and reaches the object OBJ located behind the transparent display. The observer can accordingly easily identify the object OBJ. However, it is difficult for the observer to identify the image (IMAGE) generated on the LCD panel 10 because of there is no ambient light from a light source.